1. Field of the Invention
Embodiments of the present invention relate to techniques for improving the vibrational health of computer systems. More specifically, embodiments of the present invention relate to techniques for efficiently characterizing the vibrational health of computer systems with variable internal configurations.
2. Related Art
Computer systems such as servers and storage arrays can be adversely affected by mechanical vibrations of system internal components and structures. In particular, when structural resonances are present in servers or storage arrays at some characteristic frequencies, it is likely that internal system fans or disk drives operate at some rotational frequencies that are substantially the same as one of the structural resonant frequencies. When this condition occurs, the rotational motions of the fans or the disk drives can excite a structural resonance within the computer system's mechanical structure, thereby causing destructive amplification of internal vibrations. The amplified internal vibrations can subsequently lead to degradation of throughput to hard drives, and can also accelerate other mechanical failure mechanisms.
Note that the above-described vibrational problems are becoming more significant because of the following trends in computer system manufacturing: (1) cooling fans are becoming increasingly more powerful; (2) chassis and support structures are becoming weaker because of design modifications that reduce cost and weight; and (3) internal disk drives, power supplies, and other system components are becoming more sensitive to vibration-induced degradation. Consequently, it is highly desirable to characterize the vibrational health of a computer system to identify and avoid these structural resonant frequencies.
One technique for characterizing the vibrational health of a computer system involves running a “swept sine” test on the computer system. During a swept sine test, a small vibration at a controlled frequency is generated on the computer system. This controlled frequency is swept from high values (typically from 700 KHz to 900 KHz) down to very low values (typically from 5 Hz to 10 Hz). The amplitudes of vibrations are subsequently measured at one or more locations inside the computer system, and vibration patterns are obtained to determine the existence of structural resonant frequencies. After the resonant frequencies are identified, the system can control the fan speeds or other rotational components so that the rotational frequencies do not coincide with any of the resonance frequencies.
Conventionally, the swept sine testing is performed by shipping the computer system to a facility that has a programmable shake table. Recently, a new technique has been proposed to install a built-in vibration generator inside each computer system (see U.S. patent application Ser. No. 11/787,782, entitled, “BUILT-IN SWEPT-SINE TESTING FOR A COMPUTER SYSTEM TO ASSURE VIBRATIONAL INTEGRITY,” filed on 17 Apr. 2007 by inventors Kenny C. Gross, et al.). Using this technique, it is possible to conduct the swept sine testing even when the computer system remains in the field.
Note that a computer system may have been characterized for vibrational health at the time of manufacture and may be certified to be free of amplifying resonances. However, during the lifetime of the computer system, the customer may upgrade or modify the internal configuration of the computer system, for example by upgrading memory, swapping system board, adding hard disks, or removing components that are no longer needed. Note that any of these component configuration changes can change the internal mass distribution within the computer system, thereby causing structural resonant frequencies to shift, or causing new resonant frequencies to be created. Hence, it is desirable to be able to identify structural resonant frequencies whenever the computer system has been reconfigured.
Unfortunately, it is not practical to ship a computer system to a facility with a shake table to perform a new vibrational health characterization each time that a customer upgrades or swaps internal components. Furthermore, even if a computer system is equipped with the built-in vibrational characterization capability, it is still desirable to minimize the number of times that vibrational health needs to be characterized.
Hence, what is needed is a method and an apparatus that facilitates efficient characterization of the vibrational health of a computer system for a number of internal configurations without the above-described issues.